<!DOCTYPE html>
<html>
	<head>
		<meta charset="UTF-8">
		<meta name="viewport" content="width=device-width,initial-scale=1,minimum-scale=1,maximum-scale=1,user-scalable=no" />
		<title></title>
		<style>
			*{
				margin:0;
				padding:0;
			}
			#wrap{
				/*vw视口的宽度*/
				width:100vw;
				height:100vh;
				background: red;
			}
			#wrap .top{
				width:95vw;
				height:8vh;
				background: yellow;
				margin:0 auto;
			}
		</style>
	</head>
	<body>
		<div id="wrap">
			<div class="top">123</div>
		</div>
	</body>
</html>
